The present invention relates to a method for activating a system for controlling and/or regulating operational sequences in a motor vehicle. The system includes several equal-access control units for controlling and/or regulating certain functions in the motor vehicle. The control units each have a volatile memory and a non-volatile memory including a loading routine. They are connected to one another via a time-controlled communications system.
The present invention also relates to a computer program which may be run on a computing unit, in particular a microprocessor, of a control unit for controlling and/or regulating certain functions in a motor vehicle.
Finally, the present invention also relates to a system for controlling and/or regulating operational sequences in a motor vehicle having several equal-access control units for control and/or regulation. Each control unit includes a volatile memory and a non-volatile memory including a loading routine, and are connected to one another via a time-controlled communications system.
A plurality of control devices for controlling or regulating the operational sequences in a motor vehicle are provided. These control devices, of which each controls or regulates a particular functional unit of the motor vehicle during operation, are connected to one another via a communications system. The control units are communications users of the system. One known communications system, for instance, is TTP/C (time-triggered protocol, SAE Class C) or FlexRay (a communications system under development by BMW, DaimlerChrysler, Motorola, Philips and Bosch; Information available on the Internet under http://www.flexray-group.com).
Control units may, in principle, be divided into two categories. On the one hand there are the so-called individual control units. These are control units having an individual program. They are applied, for instance, to regulating braking systems (anti-lock brake systems, ABS) or to regulating an internal combustion engine. On the other hand, control units having the same construction are provided, which are used, for example, for regulating electromechanical brakes (EMB; brake-by-wire). In the case of EMB, four control units are provided one for each wheel, which are identically constructed and operated with the same software. The four control devices fulfill the same function, namely, adjusting the braking force according to a setpoint input.
When each individual wheel is regulated, the differences come about only from the local positioning of the control unit. That is the case in a braking force distribution between front and rear axle, and in operating an ABS,ASR (drive slip regulation) or ESP (electronic stabilizing program). In those cases, the control unit has to know to which wheel it is assigned, since wheel-specific setpoint values are to be lined up.
The control units usually have a non-volatile program memory and a volatile memory. In order to simplify the programming of the control units of the system, particularly with respect to a subsequent modification of functional units of a motor vehicle controlled or regulated by the system, that part of the program which is identical for all control units may be stored in a central memory, and from there may be transmitted to the volatile memory of the individual control units, within the framework of activating the system. In the case of a subsequent modification, a program change has only to be made at one central location, namely the central memory.
Distributed systems having a time-controlled communications system are known, for example, from German Published Patent Application No. 197 53 288. They require a common global time base. This is formed with the participation of all the control units logged on to the communications system. It is known, for example, that one may form the global time base by forming the average value of all the local time bases of the control units. The control units ascertain individual differences between their local time base and the global one. In the control units the difference is added to the local time base, and the sum is used as the global time base. The process just described is called synchronization of the control units to the global time base.
However, in the case of systems, known from the related art, having several control units which are connected by a time-controlled communications system, it is difficult to bring about the activation of the system if the data required for the time-controlled communications for all the control units are stored in the central memory.
A method for operating a time-controlled communications system of Motorola is known from its xe2x80x9cDSI Bus Standard, Release 1.0xe2x80x9d. In this case, in normal operation a master control unit is required, which makes available the global time pulse to the slave control units. In order for the system to remain fully functional even during malfunctioning of the master control unit, the master control unit must be designed to be redundant. This results, however, in considerable additional costs for the hardware that is not used in the normal case. These costs may be saved in the case of systems having equal-access control units as communications users.
The present invention is based on the creation of a safe and reliable activation of a system for controlling and/or regulating operating sequences in a motor vehicle.
Starting out from the method of the species recited at the outset, the present invention proposes a method having the following method steps to achieve this object:
the system is switched on;
one of the control units temporarily becomes a master control unit;
at least one of the control units has a central memory in which data are stored that are used for the time-controlled communications for all the control units, and, during the activation process of the system, the master control unit coordinating the logging on of the remaining control units to the communications system, in particular the transmission of the data from the central memory via the communications system to the remaining control units; and
the temporary master function of the master control unit is ended upon the expiration of a predefinable time duration or at termination of the activating process.
According to the present invention it is proposed that the distributed system shall be operated using a time-controlled communications system in normal operation with equal-access communications users. Thereby, the system may be scaled and expanded without problem. In order to be able to coordinate the required sequences in the system during the activation process (revving-up), it is proposed that one of the control units temporarily assume the function of master control unit. The remaining control units are treated as slave control units during the activation process. Which control unit is drawn upon as master control unit may be determined at will.
At least one of the control units has a central memory in which data required for the time-controlled communications are stored. Within the framework of the activation of the system, these data are transmitted to the individual control units which have logged on to the communications system, and are there stored, for example, in the volatile memory. The master control unit coordinates the activation process of the system, particularly the reading out of the data from the central memory, and the transmission of the data via the communications system to the control units.
As long as one of the control units assumes the master function, the local time of the master control unit is used as the global time base for the communications system. The remaining control units are synchronized with this local time base. After the expiration of a predefinable time duration (a so-called timeout) or after termination of the activation process of the system, the master control unit gives up its master function again, and becomes an equal-access communications user, in addition to the remaining control units. In this connection, the transition is made from the local time base of the master control unit to the global time base. All the communications users are synchronized with the global time base. This is formed with the participation of all the control units logged on to the communications system. The global time may be set, for instance, by developing the average value of all the local time bases of the control units. The control units ascertain individual differences between their local time base and the global one. In the control units the difference is added to the local time base, and the sum is used as the global time base.
According to one advantageous further development of the present invention, it is proposed that a control unit having the central memory becomes the temporary master control unit.
Alternatively, it is proposed that the control unit which first terminates its own start routine after the starting of the system becomes the temporary master control unit.
According to one preferred specific embodiment of the present invention, it is proposed that each control unit, after termination of its own start routine, receive signals present in the communications system for a predefinable period. If a control unit does indeed receive signals, it is assumed that it is not the first control unit which has terminated its own start routine. For, the signals that are received by the control unit via the communications system are indeed emitted by those control units which had terminated their start routine before (this) control unit. If signals were received, after expiration of the predefinable time period, the control units transmit signals over the communications system for the purpose of logging on with the temporary master control unit as communications users.
If a control unit receives no signals, it is assumed that it is the first control unit which has terminated its own start routine. It is proposed that a control unit become the temporary master control unit if no signals were received, during this time period, from the remaining control units.
According to another advantageous further development of the present invention, it is proposed that a signal be transmitted by the temporary master control unit over the communications system, after the start of the system. The master control unit transmits the signal at the latest after terminating its own start routine. The signal may include information on which of the control units has assumed the master function (control unit-specific identifier of the master control unit), and on with which time base the remaining control units should synchronize (local time base of the master control unit). The signal may also be a request to the remaining control units to identify themselves to the master control unit and to log on to the communications system.
According to a further preferred specific embodiment of the present invention, it is proposed that the signal be transmitted by the temporary master control unit individually to the remaining control units. The definite identifications of the remaining control units are known to the master control unit, for example, by the aid of data from the communications protocol.
It is suggested alternatively that a signal from the temporary master control unit be transmitted cyclically to all the remaining control units. The signal according to this alternative specific embodiment is not intended for a specific control unit, but for all the remaining control units which have not yet logged on as communications users. Those of the remaining control units, which have terminated their start routines, receive the signal and log on as communications users with the master control unit.
The signal is advantageously received by the remaining control units and, as response to the received signal, a response signal is sent to the temporary master control unit via the communications system. Upon receipt of the response signal by one of the remaining control units, the master control unit coordinates the transmission of the data from the central memory to the corresponding control unit via the communications system. The data transmission may occur, for example, in data packets, so that the master control unit may continue to transmit signals to the remaining control units and may process the response signals of the remaining control units.
A control unit-specific identifier is preferably transmitted along with the response signal. In this manner, the master control unit is informed which of the remaining control units has logged on as a communications user. The identifier may be developed as software-related or hardware-related. For example, a connecting element for connecting a control unit to the communications system may have contact pins or terminal pins whose coding makes possible the unique identification of the control unit. The number of coded pins determines the number of possible combinations. For example, two bits are used for coding the four control units of an EMB, e.g. 00 for left front, 01 for right front, 10 for rear left and 11 for rear right.
As a further possibility for control unit-individual coding of the control units it is proposed that, after receipt of the signal by the temporary master control unit, a delay take place over a time period predefinable for the individual control unit, before the response signal is sent. The remaining control units respond, at the latest after termination of their start routines, to the signal emitted by the master control unit, using a uniquely defined skew delta_t, which is ascertained with the aid of their own unique identification i of each control unit. If the master control unit emits the signal cyclically, the remaining control units respond in at least one cycle. Besides, the skew delta_t is smaller than the cycle time T of the bus master signal divided by the maximum possible number n of the bus users. A possible algorithm for the skew delta_t is:             Δ      ⁢              xe2x80x83            ⁢      t        =          T              n        -        i        +        1              ,      xe2x80x83    ⁢                    where            ⁢              xe2x80x83            ⁢      i        ∈                  [                  0          ,          n                ]            .      
In addition it is proposed that the master control unit receive the response signals of the remaining control units, and that the data from the intermediate memory be transmitted via the communications system to those of the remaining control units whose response signals were successfully received.
In case that, first of all, the control unit which was first to finish its own start routines after the start of the system was the temporary master control unit, it is proposed that, after a predefinable time period or upon the command of the control unit having the central memory, the temporary master function be transferred to the control unit having the central memory. For the transfer of the master function, the control unit having the central memory may transmit a corresponding message via the communications system to the remaining communications users. Initialization of the system is then continued by the control unit having the central memory as described above. After transfer to it of the master function, the control unit having the central memory coordinates the necessary sequences during the remaining activation process in the system, in particular it coordinates the logging on as communications users the control units that have not yet logged on.
Within the framework of the transfer of the master function, data as to which control units have already been logged on as communications users also have to be transferred to the control unit having the central memory. The data also include statements saying to which control units data required for the time-controlled communications have already been transmitted from the central memory. Therefore, it is further suggested that, upon transfer of the master function from the control unit which, after start of the system, was the first to finish its own start routines, information as to which of the control units have already logged on to the communications system be transmitted to the control unit having the central memory. The transmission of the data may be performed in different ways:
a) Upon transfer to the control unit having the central memory, the data are explicitly transmitted by the previous master control unit to the control unit.
b) The cyclical signal sent by the previous master control unit included the data. This signal was also received by the control unit having the central memory, so that the required data are available there at the point in time of the transfer of the master function.
c) Each logged-on communications user sends its status, in particular statements as to whether it has already received the data required for the time-controlled communications from the central memory, until after the transfer of the master function.
d) Upon transfer of the master function, each communications user transmits its status again.
Implementing the method of the present invention in the form of a computer program is particularly important. The computer program may be run on a computing unit, particularly a microprocessor, of a motor vehicle control device, and is suitable for executing the method according to the present invention. In this case, therefore, the present invention is realized by way of a computer program, so that this computer program constitutes the present invention in the same way as the method for whose performance the computer program is suitable.
The computer program is advantageously stored on a storage element. In particular, an electrical storage medium, for example, a random-access memory, a read-only memory or a flash memory, may be used as the memory element. In this case, therefore, the present invention is realized by way of a computer program stored on the memory element, so that this storage element provided with the computer program constitutes the present invention in the same way as the method for whose execution the computer program is suitable.
As a further attainment of the object of the present invention, it is proposed, starting from the system for controlling and/or regulating operating sequences in a motor vehicle having several equal-access control units of the species named at the outset, that
at least one of the control units has a central memory, in which data required for the time-controlled communications are stored for all the control units;
one of the control units acts as temporary master control unit during an activating process;
during the activating process, the master control unit coordinates logging on of the remaining control units to the communications system, in particular transmission of the data from the central memory to the remaining control units via the communications system; and
the master control unit ends the temporary master function upon the expiration of a predefinable time duration or at termination of the activating process.
According to one advantageous further development of the present invention, it is proposed that a control unit having the central memory becomes the temporary master control unit.
Alternatively, it is proposed that the control unit which first terminates its own start routine after the starting of the system becomes the temporary master control unit.